1. Field of the Invention
This invention relates to apparatus for conveying articles, and more particularly to apparatus for conveying wire-like members and positioning them in various treating mediums.
2. Description of the Prior Art
This invention is particularly suited for use in the manufacture of electrical components having elongated bodies and axially extending leads, such as sealed contacts. A sealed contact of the dry-reed type, sometimes referred to as a "dry-reed switch," includes two flexible leads sealed into an elongated glass envelope. Each lead has a terminal portion extending out of an end of the envelope and a contact portion extending from such end into the envelope, so that the internal contact portions of the leads overlap axially, but are spaced transversely a small distance to establish a gap therebetween.
While this invention is adapted for forming layers of metals on a variety of different articles and for solder coating, conveying, heating and positioning them, it will be particularly described with respect to an article having an elongated body and a pair of leads extending axially from each end, such as a sealed contact. However, it is to be understood that other articles, such as resistors, diodes, etc., may have metals formed on them, or may be solder coated, conveyed, heated and positioned, in accordance with this invention.
After a sealed contact has been fabricated, it is often necessary to coat the axially extending leads with solder to protect them from contamination and enhance their solderability into circuits. Certain difficulties have been encountered with the prior art techniques.
For example, in barrel plating of sealed contacts, often the leads have been bent and metal has been plated over contaminants on the leads. This interferes with the subsequent handling and assembling of the contacts with automatic equipment. While the leads may not be as readily bent in rack plating, still metal has often been plated over contaminants.
In dip and wave solder coating, the glass envelopes have often been subjected to thermoshock, damaging the glass envelopes. With these coating techniques, there is also inadequate control over the thickness of the coating on the leads.
Moreover, when the contacts are inserted into printed circuit boards, their gaps must be aligned within certain limits. Accordingly, it is desirable to have not only a controlled thickness of solder on the side surfaces of the leads, but also on the ends of the leads. Solder spikes on the ends of the leads, such as those caused by dip and wave soldering, cannot be tolerated.
In solder coating these leads, it is also desirable to not only minimize the heat applied to the sealed contacts but also to the article handling mechanisms to prevent heat damage to the glass envelopes as well as these mechanisms. In other words, to the greatest extent possible it is desirable to concentrate the heat on the leads.
It is also desirable to minimize the contact between a treating medium, such as a cleaning bath, and these mechanisms. The reason is that the medium may damage the mechanisms or interfere with their lubricants, and the mechanisms and lubricants may tend to increase the contamination of the treating medium. By minimizing this contact, especially if the medium is a liquid, any drag out of the treating medium is also reduced.
After the solder coating of the leads, it is desirable to remove any residual flux from the leads, since it may interfere with subsequent electrical contact to the leads. To do this, both longitudinal and angular control of the leads through the various treating mediums, such as a cleaning bath, is desirable. Preferably, this control should be effectuated with a simple mechanism that minimizes article handling. Minimizing such handling tends to reduce the likelihood of not only mechanical damage but also electrical damage to the contacts.
Finally, it is also desirable to effectuate the solder coating at great speeds to increase the output of the solder coating facilities.